Process for improving properties of vulcanized elastomers

ABSTRACT

VULCANIZABLE ELASTOMERIC COMPOSITIONS IN WHICH THE RUBER IS A HALOGEN-FREE POLYMER AND WHICH CONTAIN AT LEAST ONE REINFORCING FILLER AND SULFUR ARE VULCANIZED IN THE PRESENCE OF AN EFFECTIVE AMOUNT OF AT LEAST ONE SUBSTITUTED S-TRIAZINE COMPOUND ADAPTED TO MODIFY THE REINFORCING EFFECTT OF THE FILLER, THE SAID S-TRIAZINE COMPOUND HAVING THE FORMULA   (R1-N(-R2)-),(R3-N(-R4)-),(X-S-)-1,3,5-TRIAZINE   WHEREIN R1, R2, R3 AND R4 MAY BE HYDROXY OR CYANO OR HYDROGEN OR ONE OF THE ORGANIC RADICALS FURTHER DEFINED IN THE SPECIFICATION AND   X IS -N(-R6)-R7   WHEREIN R IS ALKYL AND R6 AND R7 ARE ALSO RADICALS, PRINCIPALLY ORGANIC RADICALS AS DEFINED BELOW. THE VULCANIZATES OBTAINED BY THE METHOD OF THE INVENTION ARE DISTINGUISHED BY LONGER MOONEY SCORCH TIMES, HIGHER TENSILE STRENGTH AND A HIGHER MODULUS, PARTICULARLY AT 300% ELONGATION, AS WELL AS OTHER FAVORABLE PROPERTIES.

United States PatentOflice 3,801,537 Patented Apr. 2, 1974 3,801,537 PROCESS FOR IMPROVING PROPERTIES OF VULCANIZED ELASTOMERS Hermann Westlinning, Kleinostheim, Siegfried Wolff,

Cologne, and Werner Schwarze, Frankfurt, Germany, assignors to Deutsche Goldund Silber-Scheideanstalt vormals Roessler, Frankfurt am Main, Germany No Drawing. Application Mar. 8, 1971, Ser. No. 122,190,

which is a continuation-impart of abandoned application Ser. No. 715,541, Mar. 25, 1968. Divided and this application Jan. 30, 1973, Ser. No. 328,107 Claims priority, application; 6Glermany, Mar. 23, 1967,

3 Int. Cl. C07d 55/20,"C08c 11/18, 11/60 US. Cl. 260-4253 ABSTRACT OF THE DISCLOSURE wherein R R R and R may be hydroxy or cyano or hydrogen or one of the organic radicals further defined in the specification and wherein R is alkyl and R and R are also radicals, principally organic radicals as defined below.

The vulcanizates obtained by the method of the invention are distinguished by longer Mooney scorch times, higher tensile strength and a higher modulus, particularly at 300% elongation, as well as other favorable properties.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a division of application Ser. No. 122,190, filed on Mar. 8, 1971, which in turn was a continuation-inpart of application Ser. No. 715,541 filed on Mar. 25, 1968 by the same inventors under the same title, and now abandoned.

BACKGROUND OF THE INVENTION It is known that the elastomer-fillet-interaction can be quantitatively ascertained with elastometers (rheometers). The advantage of this method, in contrast to formerly customary methods, is that the elastomer-filler-interaction can be ascertained separately from the cross-linking den. sity of the polymer according to the following formula aims in which Do: signifies the torque value (mkp) of the vulcanizate at time t0 D, signifies the torque value of the mixture (Dm'D 11 signifies the torque value caused by the cross-linking of a filled vulcanizate (D.,D,,), signifies the torque value caused by the cross-linking of an unfilled vulcanizate at vulcanization temperature, and

mi signifies the concentration of the filler mp signifies the concentration of the elastomer (Kautschuk and Gumrni-Kunstotfe 19th year No. 8/1966, pages 470-474).

The constant (1F comprehends the sum of all influences of a filler on the deformation behavior of the elastomer. As a consequence, 11F depends, on the one hand, on the chemical nature of the elastomeric polymer and, on the other hand, on the filler used. 11F, however, is entirely independent of the chemical structure of the cross-linking locations as these are produced with the accelerators used at the present time.

For example, when furnace black is used, the (IF value changes when going from polybutadiene to natural rubber and styrene butadiene rubber from 1.48 to 1.78 and 2.03.

On the other hand, the u value changes from 2.03 to 1.80 when going from furnace black to gas black in styrene butadiene rubber.

An increase in the (IF value causes an improvement in the service properties of the vulcanizates.

The invention therefore has the object to improve the service properties of a vulcanized rubber which contains sulfur and a reinforcing filler.

More specifically, it is the object of the invention to provide for a vulcanizing method in which the reinforcement efifect of a reinforcing filler present in the vulcanized rubber is improved in the final product.

SUMMARY OF THE INVENTION The invention resides in a method which comprises vulcanizing a vulcanizable composition containing at least one halogen-free polymeric elastomer, at least one reinforcing filler, sulfur and an effective amount of at least one substituted s-triazine compound adapted to modify the reinforcing effect of the filler, the said s-triazine compound having the formula wherein R and R are each selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, phenyl, aralkyl and substituted alkyl, alkenyl, cycloalkyl, phenyl and, aralkyl wherein the substituents are selected from the group consisting of OH, OR and CN, R being alkyl with up to 18 carbon atoms,

R and R are each selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, phenyl, aralkyl and substituted alkyl, alkenyl, cycloalkyl, phenyl and aralkyl wherein the substituents are selected from the group consisting of OH, OR and CN, R being alkyl with up to 18 carbon atoms,

. .3 X is selected from the group consisting of hydrogen,-

u X is N R being selected from the group consisting of hydrogen, alkyl, aralkyl and cycloalkyl and R" being selected from the group consisting of alkyl, aralkyl and cycloalkyl and wherein R and R' together may also form a cycloaliphatic ring having from 5 to 7 carbon atoms in the ring and from 5 to 10 carbon atoms, including lower alkyl, attached to the ring or wherein R and R may be linked by a member of the group consisting of -S- and and wherein the number of carbon atoms in R R R R R and R is as follows:

alkyl: up to 18 carbon atoms alkenyl: up to 6 carbon atoms cycloalkyl: from to 7 carbon atoms aralkyl: from 7 to 9 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the invention it was found that the elastomer-filler interaction expressed by the constant up and therefore the properties of the vulcanizates can be regulated in these types of rubber and filler by the use of substituted s-triazine compounds as described above as vulcanization agents, the structure of the substituents on the triazine ring being determinative of the change of the (1.1: value.

While the additives of the invention, the mercaptotriazines, can be used as vulcanizing agents for polychloroprene rubbers, and some of them have been used in that manner, they are in no way superior to conventional vulcanizing agents. One reason is that polychloroprene rubbers cannot be vulcanized with sulfur. Surprisingly, however, when used with natural rubber and halogenfree synthetic elastomers, they have a superior efiect on the properties of the vulcanizate. In particular they accomplish products having longer Mooney scorch times and therefore permit easier processing. The vulcanizates also have improved tensile strength and an improved modulus, particularly at 300% elongation.

The polymers used in connection with the process of the present invention are halogen-free sulfur-vulcanizable and double-bond containing homopolymers, copolymers or terpolymers. They may be, for instance, natural rubber (NR), synthetic polyisoprene (IR), polybutadiene and particularly 1,4-cis-polybutadiene (BR), emulsionor solvent-polymerized copolymers of butadiene with styrene (SBR), copolymers of butadiene with acrylonitrile (NBR),

polymers of ethylene and propylene which contain a ter- 4 the rubber-processing industry, furthermore finely divided materials which contain silica or consist thereof and which may be produced for instance by aqueous precipitation or from the gaseous phase. Furthermore useful are finely divided reinforcing oxides of the metals aluminum, zirconium, zinc and iron.

All carbon blacks can be used in the context of the invention which have a reinforcing effect on the elastomer. Preferable are carbon blacks with a particle size range from A. up to 5000 A. in conventional amounts. Preferably, the amounts are between 5 wt.-parts to 200 wt.- parts for each 100 wt.-parts of the elastomer.

The so-called reinforcing finely divided white fillers can also be employed, particularly those which contain or con sist of silica and have a particle size between 100 A. and 3500 A. The amounts are as conventional, preferably between 5 wt.-parts and 200 wt.-parts per 100 wt.-parts of elastomer.

The amount of sulfur is between 1 and 300 mmoles per 100 g. of elastomer.

The amount of the s-triazine compounds is between 0.1 and 50 mmoles per 100 g. of elastomer.

Regarding the sulfur, it will be understood that the amount of sulfur may be adjusted to obtain the desired cross-linking degree. Accordingly, various amounts of sulfur have been used in order to obtain the same cross-linking degree in the examples which follow so as to furnish comparable results regarding the properties obtained in the process of the invention.

The substituted s-triazines employed according to the invention as vulcanizing agents can be prepared by conventional methods.

For instance, the bis-alkyl amino mercapto triazines can, for example, be produced from the corresponding bisalkyl amino chlorotriazines by reaction with sodium sulfhydrate in suitable solvents, for example, glycol monoethyl ether, or dimethyl formamide, or water in the event the chlorotriazine has sufiicient solubility in water.

The disulfides of the mercapto triazines can be produced from the monomercapto triazines by oxidation, for instance, with iodine, hydrogen peroxide, potassium chloratesodium nitrate and the like. If mixed disulfides are to be produced, other methods are available. For example, an aromatic sulfene chloride can be reacted with a monomercapto triazine in an inert solvent. Also, the reaction of the sodium salt of the thioester of the sulfuric acid with the sodium salts of mercapto triazines in water can be em ployed to produce mixed disulfides (Bunte-salts).

The sulfenamides also can be produced by conventional methods, such as, for example, by reaction of triazine sulfene chlorides (produced from the mercapto triazines and chlorine in carbon tetrachloride) with an excess of amine. Also, they can be produced by the oxidation of amine salts of the mercapto triazines with sodium hypochlorite. Preferably, the following amines are employed: diethylamine, dibutylamine, cyclohexylamine, dicyclohexylamine, piperidine and morpholine.

The following will serve to illustrate the production of the substituted triazine compounds employed according to the invention with reference to a number of representative compounds.

(1) 2-ethylamino-4-diethylamino 6 mercapto triazine:

112 g. of dry sodium sulfhydrate (sulfohydride) were dissolved inlSOO ml. of glycol monoethyl ether and 299.5 g. of 2-ethylamino-4-diethylamino-6-chloro-s-triazine added thereto while stirring. The mixture was then heated and boiled under reflux for 2 hours. Thereafter the glycol monoethyl ether was distilled off under vacuum and the residue taken up in water, clarified with charcoal and filtered. The mercapto triazine was precipitated from the filtrate with acetic acid. After filtering and drying, 219 g. of the product were obtained in the form of a white. powder. Yield was 96.6% of theory.

The following representative monomercapto triazines (x=H) were obtained in an analogous manner:

the mixture heated while stirring under reflux. The mercapto went into solution with liberation of HCl. The re- Melting R: R: R: R4 point, C.

H CH H CzHri 263 H 01H H CzHI-I 271 H CzHs CzH 02H; 135 H 03H; H H; 270 H CzHr-l H CHaCHiOH 240 H CIH} H |H| 255-257 CH 0.11; CH CeH 179 CzH; 02 CI I 1 150 H CHICHlOH H CHzCHzOH 280 CHICHSOH CHzCHzOH CHQCHzOH CHaCHzOH 133-135 H CHI C2115 @2115 186 H C "H" H 015E 105-110 H 01H H C4Hl-1 245-245 H: H 02 250 H C4H9-11 H C4Hrn 250 Call 01H; H C4H9-1 137 H CgH; H C4H9-n 181 C Hn CeHu H C :H 5 248-250 H CH: H CH3CH3CH1OCH| CzH CzH H CHaCH=CHa 166-167 H C H H C H2C H 170-171 H CflHl H CH: C N 183-184 H CHaCHCN H CHZCHQCN 191-192 02H] 03H H (C Hz) :0 CH] 128-130 C3H1 C1H1 H (CH!) CH! 133-135 H CIHX] H ClHn 294-296 H CIHH H H 278-279 H CcHn C|Hu 0H" 263-265 H CaH H 224-225 (I)CH (2) Bis-(Z-diethylamino 4 anilido-triazine 6 yl) disulfide:

27.5 g. of Z-diethylamino-4-anilido-6-mercapto triazine were dissolved in 110 ml. of hot 4% aqueous NaOH and the solution cooled to 20 C. Thereafter, 64 ml. of aqueous sodium hypochlorite (116 g. NaOCl/ 1000 ml.) were slowly added. A weakly yellow precipitate was soon deposited which was filtered off, washed with dilute NaOH and with water and then dried. 23.5 g. of the desired triazine disulfide having a melting point of 98-100 C. were obtained. The yield was 86% of theory.

Other disulfides of the same type, for example, are the following which were produced in an analogous manner.

(3) 2,4-bis-ethylamino-6-n-butyldithio-triazine:

199 g. of 2,4-bis-ethylamino-6-mercapto triazine were dissolved in 2000 ml. of a V. normal solution of sodiumn-butyl-thiosulfate in H O. After several hours a precipitate was formed. The reaction mixture was allowed to stand for a further 24 hours and the precipitate then filtered off, washed and dried under vacuum. 268 g. of the white product of a melting point of 69 C. were obtained. The yield was 93.5% of theory.

(4) 2,4-bis-di-n-butylamine-6-phenyl-dithio-triazine:

36.7 g. of 2,4-bis-di-n-butylamino--mercapto triazine were suspended in 250 m1. of carbon tetrachloride and then 14.5 g. of C H SCl (prepared from thiophenol and chlorine in carbon tetrachloride) were added thereto and action was complete after one hour. After boiling down under vacuum 46.9 grams of a red brown smeary mass were obtained.

Analysis.For C H N S Calcd. (percent): S, 15.5; N, 14.7. Found (percent): S, 13.3; N, 14.6.

(5) 2,4-bis-diethylamino6-benzyl-dithio-triazine:

100 g. of 2,4-bisdiethylamino-6-mercapto-triazine were dissolved in 400 ml. of aqueous 4% NaOH and then 450 ml. of a l-molar solution of sodium benzyl thiosulfate (C H CH S.SO Na) were added all at once. An oil soon separated out which was then shaken out with methylene chloride. After the methylene chloride was distilled 01f 130.4 g. of a light yellow oil remained as residue.

Analysis.For C H N S (mol wt.=377): Calcd. (percent): C, 57.5; H, 7.2; N, 18.6; S, 16.9. Found (percent): C, 57.2; H, 7.3; N, 18.7; S, 17.1.

(6) 2,4-bis-diethylamino 6 (benzothiazol 2 yldithio)-triamine:

50 g. of the sulfone chloride of Z-mercapto-benzo-thiazole (produced from 2-mercapto benzothiazole and chlorine in CC1 were added to a solution of 63.5 g. of 2,4- bis-diethylamino-6-mercapto triazine in 500 ml. of CCl, and the mixture boiled under reflux for 4 hours. The evolution of HCl was ended and the solvent was distilled off under vacuum. g. of a brown viscous oil remained as a residue. Yield 94% of theory.

Analysis-For C H N S (mol wt.=420): Calcd. (percent): C, 51.3; H, 5.7; N, 20; S, 22.9. Found (percent): C, 50.9; H, 5.5; N, 19.7; S, 22.4.

(7) 2,4 bis diethylamino 6 cyclohexylsulfenamidotriazine:

25.4 g. of 2,4-bis-diethylamino-6-mercapto triazine were dissolved in ml. of aqueous 4% NaOH and 10 g. of cyclohexylamine were added thereto. Then 64.5 ml. of aqueous NaOCl (116 g. NaOCl/ 10 ml. H O) were added dropwise to the mixture. An oil was produced immediately which was shaken out with CH2C12- After the CHgCIg was distilled 011, 30.4 g. of a light yellow oil remained. The yield was 80.6 of theory.

Analysis. C H N S (mol wt.=341): Cale. (percent): C, 59.8; H, 6.1; N, 24.6; S, 9.4. Found (percent): C, 59.5; H, 6.0; N, 24.3; S, 9.3.

V 189' ot =l.98.1O- V 198 az =l.92.l- V 202 a =1.98.10- V 200 a =2.73.l0 V 205 a =1.95.10" V 206 at =l.92.10 V 204 ot =2.03.10- V 207 d =2.35.10 V 188 tX =1-77-10 V 208 oz =1.77.10" V 209 a =1.63.10 V 210 a =l.87.l0" V 187 a =l.44.10- V 149 u =2.37.10- V 66 a =2.02.10

When the conventional accelerator, mercapto benzothiazole, was used instead of the mercapto triazines, the (21. value was 1.69.10 whereby the use of stearic acid and zinc oxide does influence the cross-linking yield but not the 1: value.

EXAMPLE 2 (a) The following natural rubber mixtures were used:

natural rubber: 100 g.

high abrasion furnace black: 40 g.

zinc oxide: 3 g.

stearic acid. 2 g.

mercapto triazine compound: 5 mmoles. sulfur: Variable from 1.26-4.95 g.

The sulfur quantity was varied to provide the same cross-linking density in all of the vulcanizates and also the same as in the preceding example.

The following u values were found:

V 33oc =1.52.10-

V 114 a;-=2.65.10" V 102 ot =1.27.10- V 143 (lp=1.62-1O V 186 ot =1.64.l0" V 190 ot =\=2.59.10 V 189 a =3.32.10" V 192 ot =1.82.l0- V 187 a =1.63.l0 V 149 a =2.24.10 V 66 :t =-=2.81.10-

V 2025 oz =2.47.10- V 129 a =2.88.10"

When the conventional accelerator, mercapto benzothiazole was used instead of the mercapto triazines, the up value was 1.36.10- It is evident that a strong increase can be achieved in the interaction constant CLF by selection of suitable substituents in the mercapto triazine.

(b) The following 1,4-cis-polybutadiene mixtures were used:

1,4-cis-polybutadiene: 100 g.

high abrasion furnace black: 40 g. Zinc oxide: 3 g.

Stearic acid: 2 g.

Mercaptotriazine compound: 5 mmol. Sulfur: 7.5 mmol.

The following values were found:

V 186 oc =2.l5.l0' V 193 ot =2.39.10" V 191 a =Z.32.10 V 184 a =3.09.10 V 194 a =2.37.10- V 190 ot =2.33.10- V 189 0L =2.11-10 V 198w =2.08.10

10 V 196 oz =2.08.10" V 200 u =2.94.10* V 183 ot =3.19.10- V 210 aq.-=2.58.10-

EXAMPLE 3 5 mmoles of sulfur and 7.5 mmoles of the mercapto triazines were employed in a mixture of wt.-parts of butadient styrene rubber with 50 wt.-parts of high abrasion furnace black in the presence of zinc oxide and stearic acid. The mixtures were vulcanized at C. for 60 minutes. The following values were found for the modulus at 300% elongation.

With 2110 and stearic Without ZnO and stearic 1 Not measurable.

NOTE.-kp.=kilop0nds.

EXAMPLE 4 Similar results are obtained with finely divided silicas as fillers. The mercapto triazines were used in equimolecular dosages (5 mmoles) and sulfur was used in a dosage of 7.5 mmoles in mixtures of 100 wt.-parts of a butadienestyrene rubber with 50 wt.-parts of finely divided silica.

The following modulus 300% values were measured in the vulcanizates:

Kpjcmfi V 67 77 V 68 72 The following example illustrates the considerable improvement in the service properties of vulcanizates which can be achieved with the mercapto triazines:

EXAMPLE 5 The technological properties of vulcanizates obtained with conventional mixtures are compared with those attained with the following mercapto triazines.

The following recipes were used:

Grams Mixture I Mixture II Butadiene-sty'rene rubber containing 23.5%

styrene 100 100 Finely divided silica.-- 50 50 Zinc oxide 2 Stearic acid 3 Sulfur 1. 75 1. 28 Dighenyl guanidine 1. 6 Di enzothiazyl disulfide 2. 4 V 103 0. 58

The following technological property values were measured in the vulcanizates obtained with 60 minutes vulcanization at 160 C.:

Mixture Mixture I II Tensile strength, kpJcm." 209 253 Modulus 300%, kpJcmfl 61 75 Rebound, percent 34 44 Tear resistance, kpJcm-.- 14. 5 35. 9

As can be seen, a drastic improvement in tensile strength, rebound and tear resistance is attained with a slightly higher modulus 300% value despite the reduction of the quantity of accelerator employed to 1/7 with simultaneous saving on sulfur.

When the quantity of sulfur is increased to 2.56 g. in mixture II, the modulus 300% value attained is 133 kp./cm. a value which cannot be obtained with any conventional accelerator. These values are at the level customary for carbon black filled rubbers.

A saving in vulcanizing agents can also be achieved with carbon black filled natural rubber vulcanizates.

EXAMPLE 6 A natural rubber mixture with 37 wt.-parts of a semireinforcing carbon black (as is used for tire carcasses) per 100 wt.-parts rubber was on one hand vulcanized with a mixture of 0.14 wt.-parts Z-mercapto benzothiazole, 1.25 wt.-parts of dibenzothiazyl disulfide, 3 wt.-parts zinc oxide, 2 wt.-parts stearic acid, and 2.7 wt.-parts of sulfur and, on the other hand, with a mixture of 0.5 wt.-parts of V 35, 3 wt.-parts zinc oxide, 2 wt.-parts stearic acid and 1.5 wt.-parts of sulfur. Both vulcanizates had the same tensile strength, modulus 300%, rebound elasticity and permanent deformation. Upon aging in air at 100 C. for 4 days, the elongation at break of thevulcanizate obtained with the conventional accelerators was reduced from 548% to 230% and that of the vulcanizate obtained with the mercapto triazine was only reduced from 555% to 320%, showing the considerably greater resistance to aging of the latter.

EXAMPLE 7 Similar savings in vulcanizing agents can be achieved with the sulfenamide V 128.

A mixture such as is used for carcasses of truck tires consisting of 100 wt.-parts of a mixture of 80% natural rubber and 20% of isotactic polyisoprene filled with 28.5 wt.-parts of a semi-reinforcing carbon black and 0.6 wt.- parts of mercapto benzothiazole, 1.15 wt.-parts mercapto benzothiazole disulfide, and 2.5 wt.-parts of sulfur (mixture I) was compared with one in which the accelerators had been replaced with 0.7 wt.-parts of V 128 and the sulfur content had been reduced to 1.5 wt.-parts (mixture II).

After a vulcanization period of 40 minutes, the vulcanizates had the following properties:

I II

Tensile strength kpJcm. 189 187 Modulus 300%, kpJcm. 57 71 Permanent deformation after break, percent 13 12 EXAMPLE 8 A mixture consisting of 100 wt.-parts of a rubber mixture of 75% of oil extended butadiene styrene rubber and 25% of polybutadiene rubber, 60 wt.-parts of ISAF furnace black, 0.9 wt.-parts stearic acid, 0.5 wt.-parts zinc oxide, 10 wt.-parts aromatic processing oil, 3 wt.-parts antioxidant (N phenyl-N'-isopropyl-p-phenylene diamine), 1.2 wt.-parts sulfur, and 1 wt.-part of benzothiazyl-2-cyclohexylsulfenamide (mixture 1) was compared with one in which the benzothiazyl-Z-cyclohexylsulfenamide was replaced with the same quantity of V 35 (Mixture II). The mixtures were vulcanized for minutes once at 145 C. and another time at 160 C.

Vulc. Modulus kpi/fii vulcanizate of mixture I (Z vulcanizate of mixture II Two vulcanizates of 100 wt.-parts SBR, 50 wt.-parts high abrasion furnace black, 2.0 wt.-parts stearic acid, 3.0 wt.-parts zinc oxide and 1.75 wt.-parts and 1.28 wt.-parts of sulfur, respectively, one with the conventional accelerator benzothiazyl-Z-cyclohexylsulfenamide and the other with V 35, were adjusted to about the same modulus 300% and their resistance to crack growth measured.

Vulcani- Vulcanl cats I l zate II Modulus 300%, kp./cm. 189 181 Break after bends 27, 000 130, 000

1111.25 wt.-parts benzothizayl-Z-eyclohexylsulfenamide; 1.75 w1;.-parts s ur.

I 2.28 wt.-parts V 35; 1.28 wt.-parts sulfur.

One of the most important service properties of a vulcanizate is its resistance to abrasion which stands in close relationship to the polymer-filler interaction constant (1 The abrasion resistance can be increased considerably with the mercapto triazines employed according to the invention.

EXAMPLE 10 The abrasion resistance of vulcanizates produced from the following recipes were tested:

Mixtures (wt.-parts) I II III IV SBR 100 100 100 100 High abrasion furnace black 50 50 50 50 stearic acid 2 2 2 2 Zinc oxide 3 3 3 3 Aromatic processing oil 10 10 10 10 Sulfur 1. 75 1. 3 1. 0 1. 28 Benzothiazy l-2-cyclohexylsulienamide 1. 25 V 104. 1. 3 V 35 1.3 0.57

The mixtures were vulcanized for minutes at 160 C. and their relative abrasion resistance measured (H. Westlinning, Kautschuk & Gummi, 20, 1967, No. 1, pages 5-8).

Relative abrasion resistance Mixture I Mixture II Mixture III 131 Mixture 1V 162 It is known that vulcanizates with finely divided silicas as fillers only have very low abrasion resistances. Such abrasion resistance can be improved considerably by replacement of the conventional accelerators with the mercapto triazines so that practically no difierences exists between the abrasion resistance of vulcanizates filled with carbon black and those filled with finely divided silicas.

EXAMPLE 11 The vulcanizates out of the following three compositions were tested:

Mixtures (in parts by won;

I II III Butadiene styrene rubber containing 23.5%

styrene 100 100 100 High abrasion furnace black 50 Finely divided silica 50 50 fi ri a 2 2 c1 sdlfuriifl 1. 75 1. 75 1. 28 Beumthiazyl-2-cyclohexylsulfenamlde 1. 25 Dibenzothiazyl disulfide 2.4 Diphenyl guanidine. 1. 6 V 35 2.28

The relative abrasion resistance of the vulcanizates was as follows:

Relative abrasion resistance Mixture I 100 Mixture II 43 Mixture III 98 The following examples illustrate that the action of the mercapto triazines is not limited to natural rubber and butadiene rubber, but also is present in all rubber polymers of the most varied chemical compositions.

EXAMPLE 12 Wt.-parts Butyl rubber 100 High abrasion furnace black 50 Stearic acid 2.0 Zinc oxide 3.0 V143 1.13 Sulfur 2.0

Vulcanization temperature: 150 C. Vulcanization period: 80 minutes.

The following properties were obtained in the vulcanizate:

Tensile strength, kp./cm. 164 Modulus 300%, kp./cm. 56 Rebound, percent 8 Shore hardness 57 Tear resistance, kp./cm. 17

EXAMPLE 13 Wt.-parts Ethylenepropylene terpolymer rubber containing cyclopentadiene 100 High abrasion furnace black 50 Stearic acid 2.0 Zinc oxide 3.0 V 143 1.13 Sulfur 1.5

Vulcanization temperature: 150 C. Vulcanization period: 120 minutes.

The following properties were obtained in the vulcanizates:

Tensile strength, kp./cm. 156

Modulus 300%, kp./cm. 62 Rebound, percent 34 Shore hardness 62 Tear resistance, kp./crn 17 EXAMPLE 14 Wt.-parts Acrylonitrile rubber 100 High abrasion furnace black 50 Stearic acid 2.0 Zinc oxide 3.0 V 143 1.13

Sulfur 2.0 Vulcanization temperature: 150 C. Vulcanization period: 80 minutes.

14 Properties of vulcanizates Tensile strength kp./cm. 253 Modulus 300%, kp./cm. 248 Rebound, percent 19 Shore hardness 78 Tear resistance, kp./cm. 8

EXAMPLE 15 Wt.-parts 1,4-cis-polybutadiene 100 High abrasion furnace black 50 V 143 1.13 Sulfur 1.75

Vulcanization temperature: 150 C. Vulcanization period: 80 minutes.

Properties of vulcanizate Tensile strength, kp./cm. 182

The following example illustrates the desirable effects regarding heat generation during the vulcanization. Since there is a close relationship between degree of cross-linking and heat build-up under dynamic deformation, the resistance against a chemical reversion under the influence of the vulcanization temperature is shown by the following measurements.

The properties of difierent vulcanizates vulcanized as indicated at temperatures from 145 to 175 C. appear in greater detail from the following example:

EXAMPLE 16A A natural rubber base composition comprising wtparts natural rubber, 40 wt-parts of a reinforcing carbon black, 3 wt-parts of zinc oxide, 2 wt-parts of stearic acid, 2.5-wt-parts of sulfur and 0.5 wt.-part of CBS (N-cyclo hexyl-Z-benzothiazolsulfenamide) [Mixtures I] were compared with the same mixture, but, containing 0.5 wt.-part of the triazine above identified as V 143 instead of CBS (Mixture II). Both mixtures were vulcanized at temperatures between 145 C. and 175 C. The following results were obtained regarding the heat bulid-up under dynamic deformation:

Heat build-up C.)

Vulcanization Mixture I Mixture II temperature, 0. (prior art) (invention) EXAMPLE 17 Elastomeric compositions consisting of 200 wt.-parts natural rubber, 50 wt.-parts of a reinforcing carbon black, 3 wt.-parts zinc oxide, 2 wt.-parts Stearic acid, 2.5 Wt.-

parts of the sulfenamide identified above as V 307 (Mixture I) and of the sulfenamide V 309 respectively (Mixture II). The following properties were found in specimens vulcanized at 150 C. for 40 minutes:

Mixture I Mixture II Tensile strength kpJcrn. 259 258 Modulus 300%, kp./cm 165 180 Shore hardness 69 71 Rebound, percent 45' 45 EXAMPLE 18 A natural rubber composition as formulated in Example 17 was vulcanized with 0.5 wt.-part each, of the disulfides V 282 (Mixture I), V 283 (Mixture II), V 285 (Mixture III), V 286 (Mixture IV) and V 315 (Mixture V). The following properties were found in the mixtures which had been vulcanized at 150 C. at the time indicated in the preceding example:

Mixtures I II III IV V Tensile strength, kpJcm. 238 238 222 245 215 Modulus 300%, kpJcIn. 162 169 157 167 177 Shore hardness 72 73 73 74 72 Rebound, percent 41 41 39 44 42 V 282:2-ethylamino-4-diethylamino-6-benzyldithiotriazine V 283=2-ethylamino-4-diethylamino-6-ethyldithiotriazine V 285':2-amino-4-diethylarnino-6-benzyldithio-triazine V 286:-arnino-4-diethylamino-G-ethyldithio-triazine V 315=bis-(Z-diethylamino-4-t-butylamino-triazine-6- yl)-disulfide EXAMPLE 19 Mixture Mixture Tensile strength, kpJemJ 250 220 Modulus 300%, kpJemJ- 154 162 Shore hardness 70 72 Rebound, percent 41 39 EXAMPLE 20 Elastomeric compositions of the same contents as stated in the preceding example were vulcanized with 1 wt.-part, each, of the sulfenamides V 304 (Mixture I), V 306 (Mixture H), V 309 (Mixture III) and V 310 (Mixture IV). The following properties were determined after vulcanization at 160 C. for the indicated time:

Mixtures I II III IV Tensile strength, kp./em 3 231 261 247 274 Modulus 300%, kpJcm. 185 184 165 180 Shore hardness 70 71 71 69 Rebound, percent 37 39 38 40 It will be understood that the high activity of the mercaptotriazine compositions and their derivatives is also of great advantage for the industrial use in other respects, as appears from the following examples:

EXAMPLE 21 The conventional accelerators MBTS 1 and MBT 2 were 1 MBTS dibenzthlazyldisulfide. 2 MBT Z-mercaptobenzthiazole.

replaced by the same amount of V 143 in a natural rubber stock such as used for tire carcasses. The rubber stock consisted of wt.-parts natural rubber, 45 wt.-parts of a semi-reinforcing carbon black, 3 wt.-parts zinc oxide, 2 wt.-parts stearic acid, 2 wt.-parts sulfur and 0.8 wt.-parts of the accelerator MBTS and 0.4 wt.-parts of the accelerator MBT (mixture 1).

In the mixture II, containing the same amount of the accelerator V 143, the carbon black content was reduced from 45 wt.-parts to 25 wt.-parts in order to reduce the high modulus at 300 caused by the high polymer-filler interaction constant u in the presence of V 143 to the level of the modulus obtained in a mixture with the conventional accelerators. Specimens vulcanized at C. for

40 minutes showed the following properties:

Mixture I Mixture II (prior art) (invention) Tensile strength, kpJcm. 194 235 Modulus 300%, kp./cm.. 137 130 Rebound, percent. 50 71 Shore hardness 65 60 Heat build-up C. 45 18 The low heat build-up of the vulcanizates out of the mixture H containing V 143 in consequence of the reduction of the carbon black content, will particularly be noted. This low heat build-up under dynamic deformation results in a considerably cooler run for auto tires and, accordingly, in better stress properties and a longer life time.

EXAMPLE 22 The vulcanizates showed the following properties:

Tensile strength, kp./cm. 174 Modulus 300%, kp./cm. 148 Shore hardness 68 Rebound, percent 45 EXAMPLE 23 A composition consisting of 100 wt.-parts of a solventpolymerized butadiene-styrene block polymer containing about 20% styrene, 50 wt.-parts of a high abrasion furnace black, 2 wt.-parts stearic acid, 3 wt.-parts zinc oxide, and 2 wt.-parts sulfur, was vulcanized for 60 minutes at C. with 1 wt.-part V 210. The following properties were determined in the vulcanizates:

Tensile strength, kp./cm. 188 Modulus 300% kp./cm. Shore hardness 81 Rebound, percent 40 If the additive V 210 is replaced by the conventional accelerator CBS (N-cyclohexyl-Z-benzothiazol-sulfenamide) the modulus under the same vulcanization conditions is only 152 kp./cm.

The following tables show the improvement accomplished with the process of the present invention in regard to certain filler-containing elastomer compositions as compared with the lack of particular improvement in connection with chloroprene rubbers designated as neoprene, because these cannot be vulcanized with sulfur as is possible with the other elastomers.

The attached Table I shows the Mooney scorch values and the modulus values at 300% elongation for the polychloroprene. In the tests there were used conventional vulcaniz-ing agents, to wit, ethylene thiourea (trade name NA 22 or Vulkacit NVP). These tests were com- 17 pared with tests where the triazine derivative V 143 of the present invention was used. The test results show that with the two conventional cross-linking agents NA 22 and Vulkacit N-P, about twice thte modulus could be obtained than with the triazine derivative V 143.

Table H shows similar comparisons for a natural rubber stock, polyisoprene, polybutadiene and a styrene-butandiene blend. For the comparison tests, there was used in this case the triazine derivative V 143 which was contrasted with a corresponding disulfide from the thiazol accelerator group, dibenzthiazyldisulfide. The V 143 compound is bis-(2-ethylamino 4 diethylaminotriazine-G- yl)-disulfide.

The test results show that with all these elastomers the Mooney scorch times are longer and therefore the margin of safety during the processing is higher in case of use of the triazine accelerator V 143. Besides, in all these cases the tensile strength and the modulus at 300% elongation is higher. This shows that the V 143 compound results in a highly improved cross-linking action.

In general it can be said that polychloroprene requires an entirely different vulcanization system than the halogen-free elastomer, and that unexpectedly and surprising the present invention therefore obtains an impressive improvement in these halogen-free elastomers.

The test results appear from the following two tables:

Table I shows the results with the neoprene rubber stock, and Table II shows the results with the halogenfree rubber stocks in which the additives of the present invention accomplish a highly beneficial result.

TABLE I ing a vulcanizable composition containing (a) at least one halogen-free polymeric elastomer selected from the group consisting of natural rubber, polyisoprenes, polybutadienes, copolymers of butadiene and styrene, copolymers of butadiene and acrylonitrile, copolymers of isoprene and isobutylene, copolymers of ethylene, propylene and a diene hydrocarbon compound, oil extended synthetic elastomers of the forementioned types of elastomers, mixtures of said elastomers and mixtures of rubber with one or more of said elastomers, (b) at least one reinforcing filler, (c) sulfur and (d) at least one substituted s-triazine compound adapted to modify the reinforcing eifect of the filler, the said s-triazine compound being present in an amount equivalent to between 0.1 and 50 mmol. per 100 parts by weight of the polymeric elastomer and having the formula wherein R and R are each selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, phenyl, aralkyl and substituted alkyl, alkenyl, cycloalkyl, phenyl, aralkyl wherein the substituents are selected from the group consisting of OH, OR and CN, R being 'alkyl with up to 18 carbon atoms, R and R are each selected from the group consisting of hydrogen, alkyl, alkenyl, cycloalkyl, phenyl, aralkyl and substituted alkyl,

Mixture alkenyl, cycloalkyl, phenyl and aralkyl, wherem the sub- I II III IV stituents are selected from the group consisting of OH, Polychloroprene rubber (Neoprene) 100 100 100 100 OR and CN, R being alkyl with up to 18 carbon Semi-reinforcing carbon black 29 29 29 29 atoms Stearic acid 0. 5 0. 5 0. 5 0.5 Zine oxide 5 5 5 5 X 15 Magnesium oxide 2 2 2 2 Ethylenethiour 0.5 R Thioalkylperhydrotriazine. 0.5 V 143 0.5 N Mooney scorch time (min.) 11 8 8 12 Mooney cure time (min) 29 13 12 22 R7 vulcanization, 153 C./60 min; 6

Modulus 2oo%,k m,= 27 e1 62 4 R belng selected from the group consisting of hydrogen, Modulus 300%, kp /em.' 57 135 130 70 7 Show hardness 51 58 60 54 alkyl, aralkyl and cycloalkyl and R being selected from the group consisting of alkyl, aralkyl and cycloalkyl and TABLE II Mixture I II III IV V VII VII VIII Natural rubber-. 100 1,4-cis-polyisoprena 100 1,4-cls-polyb11mdienn 100 SBR copolymer 100 HAF carbon black 50 50 50 50 50 5O 50 Zinc mridn 3 3 3 3 3 3 3 3 Stearic acid 2 2 3 3 2 2 2 2 Dibenzothiazyldisnlfidn 0. 5 0. 0 0. 9 1 V1 0.5 0.6 0.9 1 Sulfur 2. 5 2. 5 2. 5 2. 5 1. 5 I. 5 2 2 Mooney scorch time (111111.) 15 27 14 21 17 23 18 23 Mooney cure time (min). 18 29 19 23 23 27 25 28 Vulcanization, 150 (3/40 Tensil strength, kp/em. 176 243 147 246 121 141 234 257 Modulus 300%, kD/em. 120 167 89 171 71 80 157 169 Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A method of improving properties of vulcanized filled elastomeric compositions which comprises vulcanizwherein R and R together may also form a cycloaliphatic ring having from 5 to 7 carbon atoms in the ring and from 5 to 10 carbon atoms, including lower alkyl, attached to the ring, or wherein R and R may be linked by a member of the group consisting of O, S and N t. and wherein the number of carbon atoms in R R R R R and R is as follows: alkyl up to 18 carbon atoms alkyl up to 18 carbon atoms cycloalkyl from 5 to 7 carbons atoms aralkyl from 7 to 9 carbon atoms.

2. The method of claim 1, in which the reinforcing filler is a carbon black having a particle size from 100 to 5000 A. and is added to the composition in an amount from 5 to 200 weight-parts per 100 weight-parts of rubber polymer.

3. The method of claim 1, in which the reinforcing filler is a finely divided white filler having a particle size from 100 to 3500 A. and is added to the composition in an amount from 5 to 200 wt.-parts per 100 wt.-parts of elastomer.

4. The method of claim 1, wherein the filler is a silica.

5. The method of claim 1, in which the vulcanizable composition contains between 1 and 300 mmol. of sulfur per 100 g. of elastomer.

20 References Cited UNITED STATES PATENTS 2,804,450 8/1957 Naylor 26092.3 2,892,807 6/1959 Sellers et a1. 260-41.5 R

ALLAN LIEBERMAN, Primary Examiner H. H. FLETCHER, Assistant Examiner US. Cl. X.R. 

